The principal objective of the proposed research is the development of the coordination chemistry of Cu(I) in order to provide model compounds of possible relevance to the structures and activity of the copper ion sites in a number of redox active copper enzymes. The structural and chemical information obtained from studies of new Cu(I) chemical systems will be used to establish the chemistry of analogous Cu(II) compounds which are derived by electron transfer and/or dioxygen reactions. This will give insight into the essential nature of (a) Cu(I)-Cu(II) redox processes, and (b) Cu(I)-O2 (dioxygen) interactions and reactions. The copper centers and enzymes of immediate interest are; (a) the type 1 copper ion in the "blue" electron carriers and oxidases, (b) the type 3 copper center in the oxidase laccase, (c) hemocyanin and tyrosinase, and (d) dopamine beta-hydroxylase. A number of common features are apparent in the nature of the copper active sites of the proteins under discussion. They are: (1) the existence of "Cu(I)-like" sites in the proteins; (2) the reduced state of copper interacts/reacts with molecular oxygen in many of the copper enzymes. Specifically, our aims for the requested period of support are to: (1) design, synthesize and characterize new copper(I) complexes of polydentate ligand systems. These will be mononuclear and polynuclear, with nitrogen and/or sulfur donor groups, having coordination numbers of two through four. Systematic studies will establish tendencies in Cu(I) chemistry. (2) Characterize analogous C(II) derivatives. Through structural, electrochemical and other characterization, establish structural-redox relationships in Cu(I)-Cu(II) systems derived by electron transfer or from oxidation (oxygenation) by O2 of Cu(I). (3) Characterize the reaction chemistry of these copper complexes. Particular emphasis will be placed upon interactions and reactions with molecular oxygen and relevant substrates (phenols and catechols). This area includes synthetic and mechanistic studies of a monooxygenase model system.